The modules listed in
/etc/mkinitcpio.conf are included in the intitrd when it is generated with
mkinitcpio -p linux. This loads the temporary filesystem into memory, and needs to include modules necessary to create this successfully, depending on your setup.
An example would be adding
raid1 to your modules line in
/etc/mkinitcpio.conf to assemble a Raid1 array.
In your modules line in
/etc/rc.conf you would only need to include modules that are not automatically loaded by
udev but that you may require to run specific applications once your filesystems are mounted, such as
Note: in the case of a Raid array, you would also include
USEDMRAID="yes" in your